Strong Sporadic E Occurrence Detected by Ground‐Based GNSS

The ionospheric sporadic E (E-s) layer has significant impact on radio wave propagation. The traditional techniques employed for E-s layer observation, for example, ionosondes, are not dense enough to resolve the morphology and dynamics of E-s layer in spatial distribution. The ground-based Global Navigation Satellite Systems (GNSS) technique is expected to shed light on the understanding of regional strong E-s occurrence, owing to the facts that the critical frequency (f(o)E(s)) of strong E-s structure is usually high enough to cause pulse-like disturbances in GNSS total electron content (TEC), and a large number of GNSS receivers have been deployed all over the world. Based on the Chinese ground-based GNSS networks, including the Crustal Movement Observation Network of China and the Beidou Ionospheric Observation Network, a large-scale strong E-s event was observed in the middle latitude of China. The strong E-s shown as a band-like structure in the southwest-northeast direction extended more than 1,000 km. By making a comparative analysis of E-s occurrences identified from the simultaneous observations by ionosondes and GNSS TEC receivers over China middle latitude statistically, we found that GNSS TEC can be well employed to observe strong E-s occurrence with a threshold value of f(o)E(s), 14 MHz.